The value of the wrapped securities that investors hold has been impaired, even where there has been no de-terioration in the underlying credit characteristics of the project, because the securities were bought bearing a yield reflective of a triple-A risk and those securities are now trading at a price, at best, which reflects the higher of the rating of the relevant monoline and the underlying rating of the project, the latter of which is generally in the triple-B to single-A category. In some cases, the underlying project does not have a public rating and little information is available to investors to make their own judgements about the projects' risk of default. In these cases, valuation is particularly difficult and many fund managers have been instructed to sell bonds issued for projects in this situation. This further drives down the value of the securities. Although most PPP bonds are owned by "buy-and-hold" investors with the result that little trading occurs and, therefore, these losses are unlikely to crystallise, funds must still recognise the impairment in value.